Style A 36 by 48 tall

1
Laser Needle Guide for the Sonic Flashlight David
Wang1,3,4, Bing Wu2,3, George Stetten1,2,3,4,5 1De
partment of Biomedical Engineering, Carnegie
Mellon University, Pittsburgh PA 15213,
USA 2Department of Psychology, Carnegie Mellon
University, Pittsburgh PA 15213, USA 3Robotics
Institute, Carnegie Mellon University, Pittsburgh
PA 15213, USA 4University of Pittsburgh Medical
Center, Pittsburgh PA 15261, USA 5Department of
Biomedical Engineering, University of Pittsburgh,
Pittsburgh PA 15261, USA
Out-of-Plane Ultrasound Guided Needle Insertion
is Difficult
Implementation of Laser Guidance
In ultrasound guided vascular access, it is often
necessary to insert a needle outside the plane of
an ultrasound scan. The tip of the needle is not
visible until it reaches the plane of the
ultrasound scan. Thus, a potential exists for the
needle to miss the target, requiring multiple
needle insertions and unnecessary trauma to the
patient. Hence a method to accurately guide the
needle to the target would be valuable.
Two lasers are used so that the mid-point of the
two spots in the virtual image determines the
destination of the needle.
Our Objective
There are only a few commercial guidance systems
for out-of-plane needle insertion. They restrict
the insertion to a fixed number of pre-determined
angles (Site-RiteTM 2) or to a second
orthogonal plane (PunctSURETM 1). To overcome
these problems, we developed a laser guidance
system that offers users the ability to perform
the insertion along an arbitrary path. The
system is based on a device called the Sonic
Flashlight 3, 4, which uses a technique called
Real-Time Tomographic Reflection, described
below.
The laser generators are placed parallel and as
close as possible to the needle so that they
flank the needle destination.
Test with Water-tank Phantom
In the picture to the right, beams from two
lasers mounted along a needle strike the mirror
(4) splitting into two sets of beams. The
reflected beams reach the flat panel monitor (1)
while the direct beams penetrate the mirror to
produce bright spots on the surface of the water
tank (3). The virtual image (2) of the spots (1)
on the flat panel monitor accurately flank the
target at its actual location in the water tank.
Real-Time Tomographic Reflection
The RTTR system functions by fixing the relative
geometry of the ultrasound transducer, the
display, and a half-silvered mirror to produce a
virtual image at the scanned anatomy within the
body. Through the mirror, the ultrasound image
is seen as if it "shines out" from the probe and
illuminates the inner tissue. Thus the system has
been referred to as the Sonic Flashlight (SF).
By keeping the lasers aimed on either side of the
target, we successfully and very easily reached
the target (depth 5cm size 1 cm).
Conclusion
(? IEEE Reproduced with permission from 5)
Whereas the Sonic Flashlight with unaltered
needles has shown good accuracy for relatively
shallow targets such as veins in the arm, the
addition of laser guidance may be appropriate for
deeper procedures such as biopsies of the liver
or kidney.
Laser Needle Guidance

• The proposed path for the needle insertion is
  shown to the operator by aiming a low-intensity
  laser at the virtual target in the SF.
• The point where the needle will enter the body
  is indicated by the laser spot on the skin.
• A part of the laser beam reflects off the
  mirror, creating another spot on the flat panel
  monitor, whose virtual image shows the
  intersection of the path with the ultrasound
  slice at the location of the proposed target.

References

1. PunctSURE Vascular Access Imaging,
   http//www.punctsure.com/punctsure_description.
   html, 2005.
2. Site-Rite Ultrasound System, http//www.dymax-us
   a.com/products.html, 2005.
3. G. Stetten, V. Chib, Overlaying Ultrasound
   Images on Direct Vision, Journal of Ultrasound
   in Medicine vol. 20, no. 3, pp. 235-240, 2001
4. Stetten G, System and Method for
   Location-Merging of Real-Time Tomographic Slice
   Images with Human Vision, U.S. Patent no.
   6,599,247, issue date, July 29, 2003.
5. Wu, B, Klatzky, RL, Shelton, D Stetten G (2005)
   Psychophysical Evaluation of In-Situ Ultrasound
   Visualization. IEEE Transactions on Visualization
   and Computer Graphics (In press).